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How do you graph #y = -cos ( x- pi/4)#?

1 Answer

You can extract various information only by looking at your function:
1] It is a cosine;
2] the #-1# in front of it tells us that the amplitude is #1# and every time we evaluate the #cos# we have to change sign;
3] The #1# in front of #x# tells us that the period is #1=(2pi)/(period)#
and #period=2pi#;
4] #-pi/4# is the starting angle or initial phase that is the angle when #x=0#;